This invention relates to an identification mark reading apparatus for reading an identification mark attached onto a moving body, and more particularly to an identification mark reading apparatus suitable for a quality test of print bar codes successively printed on a roll sheet.
In recent years, a kind of marks called a bar code are generally attached for sorting/identifying articles, documents, or the like. Bar codes are such that alphabets or numerals, etc. are represented by combination of black bars and white bars of different widths, and combinations of a series of bars are used as respective codes for optical input.
Such bar codes are printed on a roll sheet by a printing machine. For example, in the case where an offset form rotary press machine is used as the printing machine, a bar code numbering machine is attached to the letterpress printing unit. According as respective letter rings of the bar code numbering machine are rotated in a direction to increment or decrement the numeric value one by one, bar codes are successively printed onto the roll sheet.
However, there are instances where bar codes of numbers in a wrong order may be printed by the inconvenience in operation that such letter rings do not rotate at a timing where they should rotate, or adjacent letter rings rotate at the same time. Further even if letter rings normally rotate, there may occur bad printing such as faint printing, or stained printing, etc.
As the conventional method of testing print bar codes, there is a method in which several tens to several hundreds sets of print spare portions are provided at the front end of a normal sheet of paper to estimate whether or not the print bar codes of the normal paper are abnormal in dependency upon whether or not bar codes in the print spare portions are properly printed. With this method, however, since bar codes are not tested in the middle of printing a normal sheet, even if bar codes are not properly printed by an erroneous operation of the numbering machine, or the like, such an improper printing cannot be found out until the printing is completed. As a result, there was the problem that a printed roll sheet becomes wasteful for a printing time after the time point where any extraordinary state has occurred in the bar code printing.
As the method of testing bar codes on a real time basis in the middle of printing, there is a conceivable approach to make a discrimination using the technology for implementing pattern recognition to the print bar codes themselves, or numerals on the lower side of the print bar codes to automatically monitor whether or not the print bar codes are abnormal.